It is known in the art that photographic display materials are utilized for advertising as well as decorative displays of photographic images. Since these display materials are used in advertising, the image quality of the display material is critical in expressing the quality message of the product or service being advertised. Further, a photographic display image needs to be high impact, as it attempts to draw consumer attention to the display material and the desired message being conveyed. Typical applications for display material include product and service advertising in public places such as airports, buses and sports stadiums, movie posters and fine art photography. The desired attributes of a quality, high impact photographic display material are a slight blue density minimum, durability, sharpness and flatness. Cost is also important as display materials tend to be expensive compared with alternative display material technology mainly lithographic images on paper. For display materials, traditional color paper is undesirable as it suffers from a lack of durability for the handling, photoprocessing and display of large format images.
In the formation of color paper it is known that the base paper has applied thereto a layer of polymer, typically polyethylene. This layer serves to provide waterproofing to the paper, as well as providing a smooth surface on which the photosensitive layers are formed. The formation of a suitably smooth surface is difficult requiring great care and expense to ensure proper laydown and cooling of the polyethylene layers. The formation of a suitably smooth surface would also improve image quality as the display material would have more apparent blackness as the reflective properties of the improved base are more specular than the prior materials. As the whites are whiter and the blacks are blacker, there is more range in between and, therefore, contrast is enhanced. It would be desirable if a more reliable and improved surface could be formed at less expense.
Prior art photographic reflective papers comprise a melt extruded polyethylene layer which also serves as a carrier layer for optical brightener and other whitener materials as well as tint materials. It would be desirable if the optical brightener, whitener materials and tints, rather than being dispersed a single melt extruded layer of polyethylene could be concentrated nearer the surface where they would be more effective optically.
Prior art photographic transmission display materials with incorporated diffusers have light sensitive silver halide emulsions coated directly onto a gelatin coated clear polyester sheet. Incorporated diffusers are necessary to diffuse the light source used to backlight transmission display materials. Without a diffuser, the light source would reduce the quality of the image. Typically, white pigments are coated in the bottom most layer of the imaging layers. Since light sensitive silver halide emulsions tend to be yellow because of the gelatin used as a binder for photographic emulsions minimum density areas of a developed image will tend to appear yellow. A yellow white reduces the commercial value of a transmission display material because the imaging viewing public associates image quality with whiter whites as yellow white are perceived as old. It would be desirable if a transmission display material with an incorporated diffuser could have a more blue white.
Prior art photographic transmission display materials with incorporated diffusers have light sensitive silver halide emulsions coated directly onto a gelatin subbed clear polyester sheet. TiO.sub.2 is added to the bottom most layer of the imaging layers to diffuse light so well that individual elements of the illuminating bulbs utilized are not visible to the observer of the displayed image. However, coating TiO.sub.2 in the imaging layer causes manufacturing problems such as increased coating coverage which requires more coating machine drying and a reduction in coating machine productivity as the TiO.sub.2 requires additional cleaning of coating machine. Further, as higher amounts of TiO.sub.2 are used to diffuse high intensity backlighting systems, the TiO.sub.2 coated in the bottom most imaging layer causes unacceptable light scattering reducing the quality of the transmission image. It would be desirable to eliminate the TiO.sub.2 from the image layers while providing the necessary transmission properties and image quality properties.
An example of coextruded thin layer technology improvements and limitations is explained in U.S. Pat. No. 5,476,708 where it is proposed that sharpness improvements in photographic systems can be achieved by an untinted, unpigmented melt extruded thin skin made to be used under a light sensitive emulsion. It would be desirable if a thin skin under the emulsion could be both coextruded microvoided biaxially oriented to provide stiffness and a more efficient diffusing layer and tinted blue to provide the necessary color correction for the yellowness of the light sensitive silver halide imaging layer.
Prior art photographic transmission display materials, while providing excellent image quality, tend to be expensive when compared with other quality imaging technologies such as ink jet imaging, thermal dye transfer imaging, and gravure printing. Since photographic transmission display materials require an additional imaging processing step compared to alternate quality imaging systems, the cost of a transmission photographic display can be higher than other quality imaging systems. The processing equipment investment required to process photographic transmission display materials also requires consumers to typically interface with a commercial processing lab increasing time to image. It would be desirable if a high quality transmission display support could utilize nonphotographic quality imaging technologies.
Photographic transmission display materials have considerable consumer appeal as they allow images to be printed on high quality support for home or small business use. Consumer use of photographic display materials generally have been cost prohibitive since consumers typically do not have the required volume to justify the use of such materials. It would be desirable if a high quality transmission display material could be used in the home without a significant investment in equipment to print the image.